LCD devices are being widely used in a variety of fields such as televisions, personal computers, cellular phones, and digital cameras because of their characteristics, such as thin profile, lightweight, and low power consumption. According to LCD devices, optical properties such as birefringence, optical rotation, dichroism, and optical rotatory dispersion of light used for display are adjusted by controlling LC orientation by voltage application. The LCD devices are further classified based on the kind of LC drive control system. In matrix display devices, for example, electrodes are disposed in a specific pattern, and the electrodes independently control driving of LCs, which allows high-resolution image display.
Examples of the matrix display devices include passive matrix display devices and active matrix display devices. According to active matrix display devices, electrodes are disposed in a matrix pattern and lines are disposed in two mutually perpendicular directions to surround each of the electrodes. Further, a switching element is disposed at each of the intersections, and this enables the respective electrodes to be separately drive-controlled by the lines. Thus the active matrix display devices can provide high-quality display when being large-capacity devices.
Various developments on the active matrix LCD devices have been made in order to improve the display qualities, as disclosed in Patent Documents 1 to 3, for example.
An LCD device of Patent Document 1 is an AMLCD (active matrix liquid crystal display) device that is configured to include in sequence, a pixel electrode substrate, a liquid crystal layer, and a counter electrode substrate. The pixel electrode substrate is provided with pixel electrodes each of which is surrounded by mutually-perpendicular gate bus lines and drain bus lines. Further, the device includes storage capacitor electrodes as a light-shielding film on the pixel electrode substrate to prevent light leakage from spaces between the pixel electrodes and the drain bus lines, thereby minimizing margin of the light-shielding film. As a result, the LCD device has an improved aperture ratio. In Patent Document 1, a signal voltage is supplied through the drain bus line.
An LCD element of Patent Document 2 is an AMLCD element, and pixel electrodes, scanning electrode lines and signal electrode lines are disposed on one substrate constituting the LCD element, the two lines being disposed in a lattice pattern to surround each of the pixel electrodes. A light-shielding conductor extended from the scanning electrode line is disposed toward a thin film transistor along the signal electrode line, and this conductor is used to prevent light leakage from spaces between the pixel electrodes and the scanning electrode lines and also spaces between the pixel electrodes and the signal electrode lines. Thus, light leakage can be suppressed regardless of whether or not a black matrix is precisely positioned with the spaces, and the area of the black matrix also can be decreased. As a result, the LCD element has an improved aperture ratio.
An LCD device of Patent Document 3 is an AMLCD device, and one of a pixel electrode and a signal line has a bent part and at the bent part, the pixel electrodes in the width direction are covered. Thus, when the pixel electrode or the signal line has the bent part, a variation in capacitance formed between the pixel electrode and the signal line (source line), caused by misalignment between layers, can be suppressed even when the LCD device is driven by dot-reversal driving where a polarity of a source signal is reversed based on every gate line. As a result, display unevenness called shadowing, caused by the capacitance variation, can be minimized.
The LCD devices are now being rapidly developed, and in addition to the improvement in aperture ratio, improvements in black-white contrast for more excellent display qualities and characteristics of active matrix substrates of the LCD devices are desired for the LCD devices.
[Patent Document 1]
    Japanese Kokai Publication No. Hei-06-308533[Patent Document 2]    Japanese Kokai Publication No. Hei-08-160451[Patent Document 3]    Japanese Kokai Publication No. 2001-281696